When the AR and PRLR are activated it inhibits Wnt signalling and a series of gene transcription changes occur that affect cell ashesion and migration, apoptosis and proliferation. Head shape doesn't matter in the process of Androgenetic Alopecia. The threshold at which these gene transcription changes occur becomes lower with age.
The same molecular signalling changes that occur in the scalp concurrently take place in the prostate where there is no tension nor lack of blood flow. In the prostate it leads to bph and in the scalp it leads to Androgenetic Alopecia